Fittings are mass-produced items that can be manufactured in large numbers in a highly efficient manner. Cutbacks on quality, however, are not acceptable. This requires high-quality machine engineering, mold construction and process technology. In practice, “pipe connectors” are referred to as fittings which comprise a threaded end and an end that is designed for a compression-type connection.
For example, a method for manufacturing fittings of stainless steel has been known from document DE 100 31 989 A1. This method uses a matrix into which is placed a piece of piping in the form of a blank and also uses a compression mandrel into which the pipe end is pressed in order to expand the pipe end. In so doing, the pipe wall is stretched in the peripheral direction. Furthermore, a shoulder provided on the mandrel exerts an axial pressure on the front-side end of the pipe piece, so that the pipe wall is compressed in the axial direction. By means of this process, an annular bead is produced all around the pipe wall, whereby an O-ring may be placed as a seal in said bead.
Another method for the production of compression fittings, preferably consisting of copper, has been known from document DE 43 36 261 A1. This literature reference discloses a multi-step method whereby a pipe piece is placed as a blank into a divided matrix. The thusly held blank is compressed in the axial direction by means of a mandrel and is optionally somewhat widened. An annular material bead is formed all around the pipe wall of the pipe. During a subsequent step, the elevated or recessed bead is rolled from the inside with a roller moving on an orbital path in order to form a smooth perfect seat for an O-ring.
The main feature of the previously known methods was the production of fittings with a seat for an O-ring. In so doing, the fittings featured on their two ends, respectively, the same connecting technology, i.e., respectively one O-ring seat and one compression region for the connection of a pipe. However, the pipe wall is so thin that no conventional thread may be applied if a threaded end connector is to be produced.
Document DE 10 2005 014 940 A1 discloses a fitting with a threaded end connector and a compression connector that is produced by a reforming process. The greater wall thickness for the threaded end connector is produced by compression. In this case, the thread must be produced on the axially compressed material.